She is the tragic result of Miki Sayaka becoming a Witch. In episode 9, Sakura Kyoko confronts her and ends up sacrificing herself, ultimately destroying the two of them. In one of the previous timelines shown in episode 10, the remaining members of the Holy Quintet fight and defeat her, which then leads to Tomoe Mami losing her sanity after realizing they're all doomed to become witches in the future.

Also becomes a stand-like entity for Sayaka in the Rebellion movie.